284 lines
11 KiB
C++
284 lines
11 KiB
C++
// Copyright 2019 Google LLC. All Rights Reserved. This file and proprietary
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// source code may only be used and distributed under the Widevine
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// License Agreement.
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#include "oec_decrypt_fallback_chain.h"
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#include <stdint.h>
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#include <string.h>
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#include "oemcrypto_corpus_generator_helper.h"
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#include "oemcrypto_types.h"
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#include "string_conversions.h"
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namespace {
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void advance_dest_buffer(OEMCrypto_DestBufferDesc* dest_buffer, size_t bytes) {
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switch (dest_buffer->type) {
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case OEMCrypto_BufferType_Clear:
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dest_buffer->buffer.clear.clear_buffer += bytes;
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dest_buffer->buffer.clear.clear_buffer_length -= bytes;
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break;
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case OEMCrypto_BufferType_Secure:
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dest_buffer->buffer.secure.offset += bytes;
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break;
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case OEMCrypto_BufferType_Direct:
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// Nothing to do for this buffer type.
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break;
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}
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}
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void advance_iv_ctr(uint8_t (*subsample_iv)[wvoec::KEY_IV_SIZE], size_t bytes) {
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uint64_t counter;
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constexpr size_t half_iv_size = wvoec::KEY_IV_SIZE / 2;
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memcpy(&counter, &(*subsample_iv)[half_iv_size], half_iv_size);
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const size_t increment =
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bytes / wvoec::AES_128_BLOCK_SIZE; // The truncation here is intentional
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counter = wvutil::htonll64(wvutil::ntohll64(counter) + increment);
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memcpy(&(*subsample_iv)[half_iv_size], &counter, half_iv_size);
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}
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} // namespace
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namespace wvoec {
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// Decrypts the given array of samples. Handles fallback behavior correctly if
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// the OEMCrypto implementation does not accept multiple samples.
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OEMCryptoResult DecryptFallbackChain::Decrypt(
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const uint8_t* key_handle, size_t key_handle_length,
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const OEMCrypto_SampleDescription* samples, size_t samples_length,
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OEMCryptoCipherMode cipher_mode,
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const OEMCrypto_CENCEncryptPatternDesc* pattern) {
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OEMCryptoResult sts = OEMCrypto_DecryptCENC(key_handle, key_handle_length,
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samples, samples_length, pattern);
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// No need for a fallback. Abort early.
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if (sts != OEMCrypto_ERROR_BUFFER_TOO_LARGE) {
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if (ShouldGenerateCorpus()) {
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WriteDecryptCencCorpus(cipher_mode, samples, pattern, samples_length);
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}
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return sts;
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}
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// Fall back to decrypting individual samples.
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for (size_t i = 0; i < samples_length; ++i) {
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sts = DecryptSample(key_handle, key_handle_length, samples[i], cipher_mode,
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pattern);
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if (sts != OEMCrypto_SUCCESS) return sts;
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}
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return sts;
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}
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// Decrypts the given sample. Handles fallback behavior correctly if the
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// OEMCrypto implementation does not accept full samples.
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OEMCryptoResult DecryptFallbackChain::DecryptSample(
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const uint8_t* key_handle, size_t key_handle_length,
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const OEMCrypto_SampleDescription& sample, OEMCryptoCipherMode cipher_mode,
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const OEMCrypto_CENCEncryptPatternDesc* pattern) {
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OEMCryptoResult sts =
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OEMCrypto_DecryptCENC(key_handle, key_handle_length, &sample, 1, pattern);
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// No need for a fallback. Abort early.
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if (sts != OEMCrypto_ERROR_BUFFER_TOO_LARGE) {
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if (ShouldGenerateCorpus()) {
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WriteDecryptCencCorpus(cipher_mode, &sample, pattern, 1);
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}
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return sts;
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}
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// Fall back to decrypting individual subsamples.
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OEMCrypto_SampleDescription fake_sample = sample;
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for (size_t i = 0; i < sample.subsamples_length; ++i) {
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const OEMCrypto_SubSampleDescription& subsample = sample.subsamples[i];
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const size_t length =
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subsample.num_bytes_clear + subsample.num_bytes_encrypted;
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fake_sample.buffers.input_data_length = length;
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fake_sample.subsamples = &subsample;
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fake_sample.subsamples_length = 1;
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sts = DecryptSubsample(key_handle, key_handle_length, fake_sample, pattern,
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cipher_mode);
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if (sts != OEMCrypto_SUCCESS) return sts;
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fake_sample.buffers.input_data += length;
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advance_dest_buffer(&fake_sample.buffers.output_descriptor, length);
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if (cipher_mode == OEMCrypto_CipherMode_CENC) {
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advance_iv_ctr(&fake_sample.iv,
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subsample.block_offset + subsample.num_bytes_encrypted);
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}
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}
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return sts;
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}
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// Decrypts the given subsample. Handles fallback behavior correctly if the
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// OEMCrypto implementation does not accept full subsamples.
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OEMCryptoResult DecryptFallbackChain::DecryptSubsample(
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const uint8_t* key_handle, size_t key_handle_length,
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const OEMCrypto_SampleDescription& sample,
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const OEMCrypto_CENCEncryptPatternDesc* pattern,
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OEMCryptoCipherMode cipher_mode) {
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OEMCryptoResult sts =
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OEMCrypto_DecryptCENC(key_handle, key_handle_length, &sample, 1, pattern);
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// No need for a fallback. Abort early.
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if (sts != OEMCrypto_ERROR_BUFFER_TOO_LARGE) {
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if (ShouldGenerateCorpus()) {
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WriteDecryptCencCorpus(cipher_mode, &sample, pattern, 1);
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}
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return sts;
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}
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// Fall back to decrypting individual subsample halves.
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const OEMCrypto_SubSampleDescription& subsample = sample.subsamples[0];
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OEMCrypto_SampleDescription fake_sample = sample;
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OEMCrypto_SubSampleDescription fake_subsample;
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fake_sample.subsamples = &fake_subsample;
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fake_sample.subsamples_length = 1;
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if (subsample.num_bytes_clear > 0) {
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fake_sample.buffers.input_data_length = subsample.num_bytes_clear;
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fake_subsample.num_bytes_clear = subsample.num_bytes_clear;
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fake_subsample.num_bytes_encrypted = 0;
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fake_subsample.block_offset = 0;
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fake_subsample.subsample_flags = 0;
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if (subsample.subsample_flags & OEMCrypto_FirstSubsample)
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fake_subsample.subsample_flags |= OEMCrypto_FirstSubsample;
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if (subsample.subsample_flags & OEMCrypto_LastSubsample &&
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subsample.num_bytes_encrypted == 0)
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fake_subsample.subsample_flags |= OEMCrypto_LastSubsample;
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sts = DecryptSubsampleHalf(key_handle, key_handle_length, fake_sample,
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pattern, cipher_mode);
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if (sts != OEMCrypto_SUCCESS) return sts;
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// Advance the buffers for the other half, in case they're needed.
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fake_sample.buffers.input_data += subsample.num_bytes_clear;
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advance_dest_buffer(&fake_sample.buffers.output_descriptor,
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subsample.num_bytes_clear);
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}
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if (subsample.num_bytes_encrypted > 0) {
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fake_sample.buffers.input_data_length = subsample.num_bytes_encrypted;
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fake_subsample.num_bytes_clear = 0;
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fake_subsample.num_bytes_encrypted = subsample.num_bytes_encrypted;
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fake_subsample.block_offset = subsample.block_offset;
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fake_subsample.subsample_flags = 0;
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if (subsample.subsample_flags & OEMCrypto_FirstSubsample &&
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subsample.num_bytes_clear == 0)
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fake_subsample.subsample_flags |= OEMCrypto_FirstSubsample;
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if (subsample.subsample_flags & OEMCrypto_LastSubsample)
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fake_subsample.subsample_flags |= OEMCrypto_LastSubsample;
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sts = DecryptSubsampleHalf(key_handle, key_handle_length, fake_sample,
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pattern, cipher_mode);
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if (sts != OEMCrypto_SUCCESS) return sts;
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}
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return sts;
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}
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// Decrypts the given subsample half. There is no fallback behavior after this;
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// an OEMCrypto_ERROR_BUFFER_TOO_LARGE produced here will be returned to the
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// caller.
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OEMCryptoResult DecryptFallbackChain::DecryptSubsampleHalf(
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const uint8_t* key_handle, size_t key_handle_length,
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const OEMCrypto_SampleDescription& sample,
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const OEMCrypto_CENCEncryptPatternDesc* pattern,
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OEMCryptoCipherMode cipher_mode) {
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if (ShouldGenerateCorpus()) {
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WriteDecryptCencCorpus(cipher_mode, &sample, pattern, 1);
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}
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return OEMCrypto_DecryptCENC(key_handle, key_handle_length, &sample, 1,
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pattern);
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// In a real CDM, you would want some fallback here to handle the case where
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// the buffer is too big for the OEMCrypto implementation. But in the case of
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// the tests, we won't be passing a buffer that's too big unless we are trying
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// to test that failure condition, so there's no need to handle that case
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// here.
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}
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// Used for OEMCrypto Fuzzing: Corpus format is as below, let | be separator.
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// cipher_mode + pattern + sample_data for all samples |
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// input_data for all samples | subsample_data for all samples
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void WriteDecryptCencCorpus(
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OEMCryptoCipherMode cipher_mode,
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const OEMCrypto_SampleDescription* samples_description,
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const OEMCrypto_CENCEncryptPatternDesc* pattern, size_t samples_length) {
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const std::string file_name =
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GetFileName("oemcrypto_decrypt_cenc_fuzz_seed_corpus");
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// Cipher mode and Pattern.
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OEMCrypto_Decrypt_Cenc_Fuzz decrypt_cenc_fuzz_struct;
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decrypt_cenc_fuzz_struct.cipher_mode = cipher_mode;
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decrypt_cenc_fuzz_struct.pattern = *pattern;
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AppendToFile(file_name,
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reinterpret_cast<const char*>(&decrypt_cenc_fuzz_struct),
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sizeof(OEMCrypto_Decrypt_Cenc_Fuzz));
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// Sample data for all samples.
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for (size_t i = 0; i < samples_length; i++) {
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OEMCrypto_SampleDescription_Fuzz sample_description_data;
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sample_description_data.buffers.input_data_length =
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samples_description[i].buffers.input_data_length;
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sample_description_data.buffers.output_descriptor.type =
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samples_description[i].buffers.output_descriptor.type;
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switch (sample_description_data.buffers.output_descriptor.type) {
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case OEMCrypto_BufferType_Clear:
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sample_description_data.buffers.output_descriptor.buffer_config =
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samples_description[i]
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.buffers.output_descriptor.buffer.clear.clear_buffer_length;
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break;
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case OEMCrypto_BufferType_Secure:
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sample_description_data.buffers.output_descriptor.buffer_config =
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samples_description[i]
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.buffers.output_descriptor.buffer.secure.secure_buffer_length;
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break;
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case OEMCrypto_BufferType_Direct:
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sample_description_data.buffers.output_descriptor.buffer_config =
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samples_description[i]
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.buffers.output_descriptor.buffer.direct.is_video;
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break;
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}
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memcpy(sample_description_data.iv, samples_description[i].iv,
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sizeof(sample_description_data.iv));
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sample_description_data.subsamples_length =
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samples_description[i].subsamples_length;
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AppendToFile(file_name,
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reinterpret_cast<const char*>(&sample_description_data),
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sizeof(OEMCrypto_SampleDescription_Fuzz));
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}
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AppendSeparator(file_name);
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// Input data for all samples.
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for (size_t i = 0; i < samples_length; i++) {
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AppendToFile(file_name,
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reinterpret_cast<const char*>(
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samples_description[i].buffers.input_data),
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samples_description[i].buffers.input_data_length);
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}
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AppendSeparator(file_name);
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// Subsample data for all samples.
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for (size_t i = 0; i < samples_length; i++) {
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for (size_t j = 0; j < samples_description[i].subsamples_length; j++) {
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AppendToFile(
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file_name,
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reinterpret_cast<const char*>(&samples_description[i].subsamples[j]),
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sizeof(OEMCrypto_SubSampleDescription));
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}
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}
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}
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} // namespace wvoec
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